When asked what could be tougher than “fire and fury,” the president responded: “we’ll see.” He also did not comment on whether the U.S. is considering a pre-emptive strike on North Korea.

“The people of this country should be very comfortable, and I will tell you this: If North Korea does anything in terms of even thinking about attack, of anybody that we love or we represent or our allies or us, they can be very, very nervous,” Trump said. “I’ll tell you why, and they should be very nervous. Because things will happen to them like they never thought possible.”

The remarks continue a series of aggressive exchanges between Trump and the North Korean regime in rhetoric more forceful than U.S. presidents typically use. As tensions escalate and Pyongyang keeps developing its nuclear and missile programs in the face of international opposition, Trump and other world leaders face a set of limited and difficult options to respond.

On Tuesday, Trump strongly warned Pyongyang against threatening the United States in a reportedly improvised line.

“North Korea best not make any more threats to the United States,” Trump told reporters, speaking slowly and deliberately with his arms crossed in front of him. “They will be met with fire and fury like the world has never seen. He has been very threatening … and as I said they will be met with fire, fury and frankly power, the likes of which this world has never seen before.”